Production of olefinic nitriles



March 1950 H. s. DAVIS ETAL 2,500,403

PRODUCTION OF OLEFINIC NITRILES Original Filed Sept. 19, 1939 2 Sheets-Sheet 1 INVENTORS ATTO R N EY March 14, 1950 H. s. DAVIS ETAL 2,500,403

PRODUCTION OF OLEFINIC NITRILES Original Filed Sept. 19, 1939 2 Sheets-Sheet 2 ATTORN EY Patented Mar. 14, 1950 UNlTED STATES PATENT OFFICE PRODUCTION OF OLEFINIC NITRILES Harold S. Davis, Greenwich, and Erwin L. Carpenter, Riverside, Conn., assignors to American Cyan-amid Company, New York, N. Y., a corporation of Maine Continuation of application Serial No. 295,618, filed September 19, 1939. This application filed September 1, 1945, Serial No. 613,990. In Canada July 23, 1940 14 Claims. (Cl. 260-4653) 1 2 The present invention relates to the production tion and/or polymerization products, and aids of oleflnic nitriles, that is those nitriles which may either as a washing or solvent medium in the be hydrolyzed to olefinic acids. removal of these products from the surface of It is known that the nitrile of acrylic acid may the catalyst. The inert liquid material further be obtained by heating ethylene cyanohydrin in 5 assists in removing these resinous by-products contact with such materials as acid sulfates, zinc from parts of the dehydration apparatus where chloride, silicic acid, metallic tin and tin comthey have a tendency to accumulate. It also pounds. Although these substances definitely assists in a more uniform transfer of heat, excatalyze the reaction, the rate of dehydration is tends the life of the catalyst, improves the yield relatively slow. Consequently, the time required of nitrile per unit of cyanohydrin added, and acts in producing a quantity of the nitrile is not as a carrier in removing the nitrile and water conducive to commercial operation. from the reaction mixture.

The principal object of this invention is to de- Fig. l of the accompanying drawings illustrates vise a method wherein olefinic nitriles may be a pot still method for the production of oleiinic readily and cheaply obtained. A further object [5 nitriles. A quantity of alkylene cyanohydrin and resides in a method for the production of olefinic a catalyst in suitable proportions is placed in the nitriles requiring only simple apparatus with high three-neck reaction vessel I, provided with a reefilciencies. flux condenser 2, stirrer 3, dropping funnel 4, and

The applicants have found that olefinic nitriles thermometer 5. The mixture is thoroughly may be readily obtained by heating the correstirred and heated to a temperature sufficient to spending alkylene cyanohydrin in the presence of produce optimum dehydration. The reflux con- 9, sufficient amount of a catalyst comprising an denser 2 containing pieces of broken glass is inorganic compound having an alkaline reaction. maintained at such a temperature that the un- The reaction using ethylene cyanohydrin as a changed cyanohydrin flows back into the reactypical starting material may be written as foltion vessel I, while the vapors of nitrile and lows: water formed in the dehydration reaction pass upward and into the condenser 6. The boiling H .ncN ht 1--.on=cHoN H0 et 1:193:51:oilydrm 8133; acrylonitrile a point of the distillate 15 recorded from thermometer T. The'liquid nitrile and water are col- The compounds which have been found lected in separate layers in the receiving vessel 8. ticularly suitable as catalysts in the dehydration A cooling head 9 contammg a llquld bollmg i a reaction are calcium oxide, calcium hydroxide, temperature approximatfely equal to the bolllng magnesium oxide, Sodium carbonate, potassium point of the nitrile obtained in the dehydration carbonate, Sodium b t and trisodium phosreaction is inserted at the top of the reflux colphate. rm umn 2 to condense such vapors of cyanohydrin The dehydration reaction may be carried out as may reach that point. The cooling head 9 is in conjunction with an inert organic compound provided with a cooling jacket ID. The process having a boiling point within the range of may be made continuous by introducing the cy- -260" C., such as petroleum fractions, naphanohydrin into the reaction vessel I by means of thalene, diphenyl ether, etc., which lowers the M- the dropping funnel 4 at a rate sufficient to maintendency of the cyanohydrin to form decompositain the course of the reaction.

Table I [Yields of acrylonitrlle from the dehydration of ethylene cyanohydrin. "Pot still method using 52 parts by weight of ethylene cyanohydrlnJ Catalyst Temp m Inert Liquid Carrier Yield Per Example Reactign cent of Name Partsbywt. vessel Name Parts byWt. Them'y 1 CaO 22.1 -180 None n5 2 CaO 26.7 -100 .do 62 a M10 10.3 220 .do :2 4 CaO 21.0 -200 Pcztlrsn lcim Fraction 185- 100 79 s cs0 09.0 185-200 ..do 100 84 a Ca(OH)r.-- 20.0 zoo-21o .do 54 15 7 N11100:-.- aao 205-215 do 51 79 Fig. 2 illustrates a reflux tower method for the continuous production of olefinic nitriles in which the dehydration reaction is carried'out in the distilling column i l containing the catalyst l2 supported on an inert material 13 such as chips of brick, pumice, coke, porcelain and the like and preferably held in place by a cylindrical metal screen basket M. The alkylene cyanohydrin which is added through the dropping funnel l5 enters the top of the column H and passes down over the catalyst. An electric heating element i6 provided with a suitable insulating jacket I! heats the column H to a temperature suflicient to promote optimum dehydration. A high-boiling inert carrier 18, such as a petroleum fraction-boiling-point range of 185-215" C., naphthalene or diphenyl ether, is heated to boiling temperature in vessel H! by means of burner 20. The inert carrier vapors enter opening 2|, reflux in the column H and continually remove the polymer from the reaction zone. In this manner the polymer is washed downward from the column ll and collectedin the vessel l9. Accordingly, the surface of the catalyst is kept comparatively clean and interaction between the polymer and fresh cyanohydrin is minimized.

The inert refluxing liquid supplies sufiicient heat to remove the vapors or' nitrile and water as fast as they are formed and thus prevents overheating of the cyanohydrin.

A fractionating tower 22 at the top of the distilling column refluxes back the inert carrier and unreacted cyanohydrin. The nitrile and Water pass over to the condenser 23 and after condensation separate into two layers in the receiving vessel 25. A cooling head 25 containing a liquid boiling at a temmrature approximately equal to the boiling point of the nitrile obtained in the dehydration reaction is inserted at the top of the fractionating tower to condense any vapors of the inert carrier or cyanohydrin as may reach that point. The cooling head 25 is provided with a cooling jacket 25.

The reflux tower method may be operated without the use of the inert liquid carrier. In this manner, the polymer which is molten at the reflux tower operating temperature will flow downward from the reaction zone and be collected in the vessel I9 attached to the base of the distilling column ll. Provision is made at the base of the still for the removal of either the polymer 2? or a mixture of the polymer and inert carrier.

A catalyst which has become inactive. due possibly to contact with the polymer may be regenerated by passing hot water and steam through the distilling column, thereby removing the poly= mer which is water soluble.

and 20 grams of anhydrous sodium borate was stirred and heated to a temperature of 190-210" C. in the reaction vessel of Fig. 1. As acrylonitrile and water were evolved, more ethylene cyanohydrin was added through the dropping funnel to maintain between 150-250 grams or the cyanohydrin in the reaction vessel. At the end of four hours,.the addition of ethylene cyanohydrln was stopped, at which point a total of 1172 grams was added. The run was continued for another hour to complete the dehydration of the remaining cyanohydrin. A brown residue of polymer and sodium borate remained which was fluid when hot, and water soluble. The yield of acrylonitrlle was 76%. The product was a colorless, mobile liquid having a boiling point of 77.3-77.5 C. at a pressure of I mm.

Example 18.

A charge of 443 grams of propylene cyanohydrin (p-hydroxybutyronitrile) and 30 grams of anhydrous sodium borate was stirred and heated at a temperature of 180-200 C. in the reaction vessel of Fig. 1. The dehydration reaction was completed in approximately five hours. The distillate separated into a water layer and a crotononitrile (,B-methylacrylonitrile) layer in the proportion of about one part of water to four parts of nitrile by volume. After removal of the water layer, the nitrile was subjected to fractional distillation and found to be a mixture of cisand transisomers of crotonic nitrlle. About 70% of the product was cis-crotonic nitrile, a waterwhite liquid having a boilin point of 107.5-108.5 C. at 760 mm. pressure. The trans-crotonic nitrile was also a water-white liquid having a boiling point of l19.0-l20.5 C. at 760 mm. pressure.

Example 19 A charge of 384 grams of propylene cyanohydrin (s-hydroxybutyronitrile) and 46 grams of trisodium phosphate was stirred and heated at a temperature of 165-190 (Lin the reaction vessel of Fig. 1. The dehydration reaction was complete in approximately four hours. The distillate was separated and the crotonic nitrile distilled as described in Example 18. The yield of crotonic nitrile (B-methylacrylonitrile) was 76.5% of theory.

Example 20 A charge of 100 grams of isobutylene cyanohydrin (,6-hydroxyisovaleronitrile) and 10 grams of anhydrous sodium borate was stirred and heated at a temperature of approximately 165 C., in the reaction vessel of Fig. 1. The material showed no coloration during the dehydration reaction, and no evidence of polymer was found at the end Table II [Continuous dehydration of ethylene cyanohydrin by "reflux tower" method} Rate of Grams oi Addition Per Cent Ethylene Inert Liquid E is of Ethylene Catalyst Yield oi ramp rgggf Cyanohydrln, Carrier Acrylonitrile c.c./min.

360 1.0 Diphenylethen. 2, 775 1.6-1.9 do 72 l, 420 l. 7-1. 9 Naphthalene l, 772 Z. 6 84 1,021 2. 8 86 899 2. 1 81 880 2. 4-2. 5 87 l, 374 4. 8-4. 9 8O 956 4. 0 NmCO; on brick 84 Example 17 of the run. The distillate was subjected to frac- A charge of 250 grams of ethylene cyanohydrin tional distillation. p,p-dimethylacrylonitrile was obtained as a water-white liquid having a boiling point of 140-142 C. at 766 mm. pressure.

Similarly other members of the olefinic nitrile series may be obtained by using as a starting material the corresponding alkylene cyanohydrin and heating the same with a dehydrating catalyst of the class herein described.

The products thus obtained readily stratify,

into two layers, the lower of which is predominantly water containing some nitrile, while the upper layer is predominantly nitrile containing some water. I

The water may be removed from the upper layer by distillation due to the fact that these nitriles can form a-zeotropic mixtures with water. Upon such distillation all the water comes over with the first portion of the distillate leaving anhydrous nitrile in the distillation vessel.

The nitrile may be removed from the lower layer by extraction with such nitrile solvents as toluene or xylene followed by fractionation of the extract.

While the invention has been described with particular reference to specific embodiments, it is to be understood that it is not to be limited thereto but is to be construed broadly and restricted solely by the scope of the appended claims.

This application is a continuation of applicants' copending application Serial No. 295,618, filed September 19, 1939, now abandoned.

We claim: I

1. A method of making an olefinic nitrile which includes the steps of heating the corresponding alkylene cyanohydrin in the presence of a sufficient amount of a catalyst comprising an alkali forming metal compound having an alkaline reaction so as to cause dehydration of the alkylene cyanohydrin.

2. The method of claim 1 in which the alkylene cyanohydrin and catalyst are heated together in conjunction with an inert organic carrier having a boiling point within the range of 130-260 C.

3. A method 01' making acrylonitrile which includes the steps of heating ethylene cyanohydrin in the presence of a sufilcient amount of a catalyst comprising an alkali forming metal compound having an alkaline reaction so as to cause dehydration of the ethylene cyanohydrin.

4. A method of making B-methylacrylonitrile which includes the steps of heating fi-hydroxybutyronitrile in the presence of a suflicient amount of a catalyst comprising an alkali-forming metal compound having an alkaline reaction so as to cause dehydration of the B-hydroxybutyronitrile.

5. A method of makin fi.fi-dimethylacrylonitrile which includes the steps of heating p-hydroxyisovaleronitrile in the presence of a sumcient amount of a catalyst comprising an alkaliforming metal compound having an alkaline reaction so as to cause dehydration of the fl-hydroxyisovaleronitrile.

6. A method of making acrylonitrile which includes the steps of heating ethylene cyanohydrin in an inert organic carrier having a boiling point within the range of 130 to 260 C., in the presence of a suflicient amount of a catalyst comprising an alkali forming metal compound having an alkaline reaction so as to cause dehy- 7 dration of the ethylene cyanohydrin.

7. A method of making p-methacrylic nitrile which includes the steps of heating p-hydroxybutyronitrile in an inert organic carrier having a boiling point within the range of to 260 C., in the presence of a suilicient amount of a catalyst comprising an alkali forming metal com pound having an alkaline reaction so as to cause dehydration of the fl-hydroxybutyronitrile.

8. A method of making 3,5-dimethylacrylonitrile which includes the steps of heating fi-hydroxyisovaleronitrile in an inert organic carrier having a boiling point within the range of 130 to 260 C. in the presence of a sufiicient amount of a catalyst comprising an alkali forming metal compound having an alkaline reaction so as to cause dehydration of the B-hydroxyisovaleronitrile.

9. A method of making acrylonitrile which includes the steps of heating ethylene cyanohydrin in a naphthalene carrier in the presence of sodium borate as a catalyst.

10. The method of making p-methacrylic nitrile which includes the steps of heating B-hydroxybutyronitrile in a naphthalene carrier in the presence of sodium borate as a catalyst.

11. A method of making p,p-dimethylacrylonitrile which includes the steps of heating ,Q-hydroxyisovaleronitrile in a naphthalene carrier in the presence of sodium borate as a catalyst.

12. A method of making acrylonitrile which includes the steps of heating ethylene cyanohydrin in the presence of a suflicient amount of sodium borate so as to cause dehydration of the ethylene cyanohydrin.

13. A method of making acrylonitrile which includes the steps of heating ethylene cyanohydrin within the range of 130 to 260 C. in the presence of a sufiicient amount of sodium borate so as to cause dehydration of the ethylene cyanohydrin.

14. A method of making an olefinic nitrile which includes the steps of heating the corresponding alkylene cyanohydrin in the presence of a sumcient amount of sodium borate so as to cause dehydration of the alkylene cyanohydrin.

HAROLD S. DAVIS. ERWIN L. CARPENTER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Erlenmeyer, Liebigs Annalen, vol. 191, pp. 269-285 (1878).

Van der Burg, Rec. Trav. Chim., vol 41, pg. 23 (1922). 

1. A METHOD OF MAKING AN OLEFINIC NITRILE WHICH INCLUDES THE STEPS OF HEATING THE CORRESPONDING ALKYLENE CYANOHYDRIN IN THE PRESENCE OF A SUFFICIENT AMOUNT OF A CATALYST COMPRISING AN ALKALI FORMING METAL COMPOUND HAVING AN ALKALINE REACTION SO AS TO CAUSE DEHYDRATION OF THE ALKYLENE CYANOHYDRIN. 